Synthetic polyamide textile material having a polyorganosiloxane grafted thereto



United States Patent No Drawing. Fiied Sept. 28, 1961, Ser. No. 141,304

5 Claims. (Cl. 8115.5)

This application is a continuation-impart of application Serial No.500,033, filed April 7, 1955, which is now abandoned.

This invention relates to a process and product. More particularly itconcerns a process forgraft copolymerizing a polyorganosiloxane to atextile produced from a polyamide and the product formed thereby.

It is an object of the present invention to provide a process for graftcopolymerizing a polyorganosiloxane to a textile produced from apolyamide.

Another object is to provide a novel and useful textile formed from apolyamide substrate to which a polyorganosiloxane is graftcopolymerized, thereby rendering the said textile water repellent.

These and other objects will become apparent in the course of thefollowing specification and claims.

In accordance with the present invention, a textile produced from apolyamide of fiber-forming molecular weight in intimate contact with apolyorganosi-loxane, is subjected to ionizing radiation to produce graftcopolymerization between the textileand the polyorganosiloxane.

By ionizing radiation is meant radiation with sufficient energy toremove an electron from a gas atom, forming an ion pair; this requiresan energy of about 32 electron volts (ev.) for each ion pair formed.This radiation has sufiicient energy to non-selectively break chemi calbonds; thus in round numbers radiation with energy of 50 ev. and aboveis effective for the process of this invention. The ionizing radiationpreferred for forming free radicals and initiating grafting on thesynthetic linear condensation polymer of this invention is high energyionizing radiation, and has an energy equivalent to at least 0.1 millionelectron volts (mev.). Higher energies (10 to 15 mev.) are even moreeffective; the only known upper limit is imposed by available equipment.This radiation is generally classed in two types: high energy particleradiation, and high energy ionizing electromagnetic radiation. Theeffect produced by these two types of radiation is similar, theessential requisite being that the incident particles or photons havesufficent energy to break chemical bonds and generate free radicals.

By high energy particle radiation is meant an emission of high energyelectrons or nuclear particles such as protons, neutrons, alphaparticles, deuterons, or the like, directed so that the said particleimpinges upon the solid polymer bearing the unsaturated amide. Thecharged particles may be accelerated to high speeds by means of asuitable voltage gradient, using such devices as a resonant cavityaccelerator, a Van de Graatf generator, a beta-tron, a synchrotron,cyclotron, or the like, as is well-known to those skilled in the art.Neutron radiation may be produced by bombardment of selected light metal(e.g. beryllium) targets with high energy positive particles. Inaddition, particles radiation suitable for carrying out the process ofthe invention may be obtained from an atomic pile or from radioactiveisotopes or from other natural or artificial radioactive material.

By high energy ionizing electromagnetic radiation is meant radiationproduced when a metal target (e.g., gold or tungsten) is bombarded byelectrons possessing appropriate energy. Such energy is imparted toelectrons by accelerating potentials in excess of 0.1 million electronvolts (mev.), with 0.5 mev. and over preferred. In addition to X-raysproduced as indicated above, ionizing electromagnetic radiation suitablefor carrying out the process of the invention may be obtained from anuclear reactor (pile) or from naturalor artificial radioactivemateriabfor example, cobalt 60. in all of these latter cases, theradiation is conventionallywt rned garnma rays.

The irradiation is carried out using a Vande Graatf electron acceleratorwith an accelerating potential of 2 million electron volts (mev.) with atube current of 250 to 290 microamperes. Samples to be irradiated areplaced on a conveyor and traversed back and forth under the electronbeam at a distance of tube window to sample of 10 cm. The conveyor speedis 40 inches per min-i ute. At the sample location the irradiationintensity is 125 watt sec/cm. of sample which is approximatelyequivalent to an available dose per pass of one mrad.

By the term textile produced from a polyamide" is meant a fabric, fiber,filament, yarn, pellicle, flock and the like produced from alinear'polyamide containing recurring units of the formula: 1

0 -Nz-( iwherein Z is a member of the class consisting of a divalenthydrocarbon radical and a divalent radical of the formula I t H O rmitt-.-

wherein G and G are divalent hydrocarbon radicals. Typical polyamidesand processes for their production are described in United StatesPatents Nos. 2,071,250, 2,071,- 253 and 2,130,948. Among the specificpolyamides in eluded Within. the present invention are those formed bythe condensation polymerization of a dibasic acid or an amide-formingderivative thereof, such as adipic, sebacic, suberic, azelaic acids orthe like, and a diamine such as piperazine, bis-amino cyclohexane,ethylene, tetramethylene, pentamethylene, fhexamethylene, decamethylene,paraxylylene diamines and the. like. Such materials may also be formedbyother, well. known methods such as by polymerization of amino acids orcaprolactam. j The following example is cited to illustrate. theinvention. It is not intended to ilimit it in any manner. The

standard washing to which samples are subjected consists of a 30-minuteimmersion in 70 C. water containing 0.5% of detergent (sold under thetrademark Tide by Procter & Gamble Co. of Cincinnati, Ohio), in anagitation washer. Radiation dosages are given in units of mrep (millionsof roentgen equivalents physical), a rep being the amount of high energyfparticle radiation which results in an energy absorption of 83.3 ergsper gram of water or equivalent absorbing material.

Example A sample of fabric woven into a taffeta weave from 70 denierpolyhexamethy-lene adipamide continuous filament having a denier perfilament of 0.2 is immersed in a liquid polydimet-hyl siloxane (DC Fluid550, manufactured by Dow-Corning Corporation of Midland, Mich.). Aftersqueezing out the excess liquid, but while still wet, it is enclosed inan aluminum foil wraper and subjected to electron irradiation in a 1mev. resonant transformed with a ibeam-out current of 560 microarnperes.The sample is placed on a conveyor belt which carries it through theelectron beam at a rate of 16 inches per minute. At the sample location,the beam supplies irradiation of 6.7 10 reps (6.7 mrep) per pass. Thesample is traversed back and forth across the beam until a total dose of40 mrep is attained, thereby graft copolymerizing the polyonganosiloxaneto the polyamide. After 15 consecutive standard washings, the sample isdried and tested for ease of wetting by placing a 0.3 inch diameter dropof water on the dry fabric and measuring the diameter of the Wet spotafter 60 seconds. The water drop on the siloxane coated, irradiatedsample spreads to a diameter of 0.5 inch. A drop on an uncoated,irradiated comparative control spreads to 1.5 inch. Repetition of theprocess substituting X-rays for particle irradiation to an equivalentdosage produces a similarly water-repellent graft copolymerized product.A sample of the fabric treated with the silicone oil (but notirradiated) and thereafter subjected to 15 consecutive standard washingshas no greater water repellency than the original, uncoated fabric.About 0.001% by weight, based on the graft-copolymerized textile, ofgraft copolymerized polyorganosiloxane is adequate to produce some waterrepellency. Grafting to produce at least about 0.01% grafterpolyorganosiloxane is preferred. Higher weight gains of 1%, or even 15%may sometimes be desirable, especially for polymer blends.

The textile to which the polyorganosiloxane is graft copolymerized actsas a substrate, the graft copolymerization being evidenced by failure ofsolvents to thereafter separate the polya-mide and polyorganosiloxaneconstituents. The shape of the polyamide textile to which thepolyorganosiloxane is adhered is not critical. Thus the process of thepresent invention may be applied to a funicular structure such as acontinuous filament, a spun yarn, staple, or the like. It may likewisebe applied to a pellicle or a fabric of ordered or randon intertwinedreticulation such as Woven, knitted, plaited, twisted, felted, fused orother construction. Furthermore, the shaped article may be in the formof finely comminuted particles which may, after having thepolyorganosiloxane adhered to it, be melted and shaped by extrusion,molding or casting, into a different form.

In the practice of the present invention, it is not necessary that thepolyorganosiloxane be coated upon the po'lyamide textile. The polyamideresin and the polyorganosiloxane can be mixed by milling or the like andthen exposed to ionizing irradiation after forming of the textilestructure or (if a drawable fiber or film) after drawing, wherebyadherence is induced. Similarly the polyorganosiloxane may equally wellbe added to the polyamide in the melt or in solution, the substrateshaped by extrusion, molding or casting and the graft copolymerizationmay then be developed by ionizing irradiation of the shaped article aspreviously described. It is obvious that any of the above methods ofapplication will produce a polymeric textile material with the modifierdispersed throughout and adhered to the organic polymeric matrix.

The polyorganosiloxanes which are employed in the present invention arecommonly referred to as silicone fluids. These materials are well knownand are more fully described in the book An Introduction to theChemistry of the Silicones by E. G. Rochow (John Wiley '& Sons, Inc.,New York, 2nd ed., 1951). Among the useful representations of thesilicones is the followmg:

wherein the Rs represent the same or different hydrocarbon radical suchas the members of the class consisting of the alkyl, aryl, alkyla'ryl,and aralkyl radicals and n is a number greater than 1 and having adegree of polymeriztion such that the polyorganosiloxane is fluid at atemperature below about 150 C. Mixtures of varying c'hain length aresuitable. The orientation and nature of the various hydrocarbonSUlbStltUEHiS in the molecular structure has not been found to be ofimportance, however it is preferred that the siloxane chain is of atleast sufficient length to be a liquid. Those poly- -organosiloxaneshaving branched, cross-linked structures, indicated by partial formulas:

The Rs in the formula may be all the same or may be different dependingupon the method of preparation. Furthermore, these Rs may containreactive groups or may be readily susceptible to oxidation, such thatheating the silicone causes it to react further to form a morecompletely cross-linked structure which is insoluble and infusible, i.e.the silicone is thermoset.

It has been observed that irradiation of the coated textiles in thepresence of air or moisture may increase the susceptibility of theproduct to degrade. This can be avoided by employing an atmosphere ofinert gas around the article while it is being irradiated.Alternatively, a satisfactory and simpler approach to wrap the sample ina material which is substantially air and Water impervious, thuslimiting the quantity of air or moisture contacting the sample. Thesamples may be wrapped in polyethylene film. The nature of such wrappingmaterial is not critical, provided it is substantially impervious to airand moisture. Aluminum foil is satisfactory.

It is within the scope of this invention to include in the combinationto be irradiated, materials which may have a protective or antioxidanteffect in preventing radiation degradation of either modifier orsubstrate or both. Compounds of this type are cysteine, carbon and thelike. It is also within the scope of the invention to include in thecombination to be irradiated materials which absorb radiation andtransmit the energy thus absorbed to the modifier or the organicpolymeric materials or both, whereby adhering is promoted and theefficiency of utilization of radiation is increased. Compounds With thisproperty are somewhat similar to sensitizers in photography, except thatin this case useful materials absorb high energy radiation and emit theenergy in a lower or more usable range. Phosphor screens containingcalcium tungstate, zinc sulfide or metallic lead or the like haveutility for this purpose. The phosphor materials may be used as platescontacting the material being treated, or may be incorporated in themodifying agent or even be coated on or dispersed in the organicpolymeric material which it is desired to modify.

The irradiation may be accomplished over a wide range of temperatures.However, a low temperature decreases the tendency toward oxidation.Since the absorption of the radiations frequently causes a temperatureincrease in the range of about 2 C. for each mrep absorbed, if high tubecurrent is employed so that absorption is complete within a short timeinterval, it is usually advisable to provide means to remove the heatgenerated to avoid injury to the sample. The use of Dry Ice to maintaina cold atmosphere is very satisfactory for this purpose. In general,irradiation at a higher temperature promotes the speed with whichbonding occurs, thus promoting a higher throughput of a given piece ofequipment at a constant radiation dosage. Temperatures as low as 80 C.and as high as 150 C. may be employed. Maintenance of the temperature ofthe sample within the range of from about to about 75 C. is preferred.

In determining the optimum dose of irradiation for any particularcombination, both the nature of the polyorganosiloxane and the nature ofthe polyamide textile must be considered. For those polyorganosiloxaneshaving one or more substituent R groups containing units of aliphaticunsaturation, irradiation dose of 0.05 mrep is usually sufiicient toinitiate the grafting reaction. Better results are usually obtained at adose of 0.1 mrep. For non-polymerizable, saturated polyorganosiloxanes aminimum dose of one mrep is recommended. In general, a dose of aboutmrep is adequate to initiate the bonding. It is preferred to use atleast a dosage of about 15 mrep. Higher dosages may be used and arefrequently highly beneficial. Dosages so high that substantialdegradation of the shaped substrate occurs must obviously be avoided. Asa guide in this regard, fibers produced from polyhexamethylene adipamidemay be irradiated to a dosage as high as 80 mrep. However, it ispreferred that the dosage applied to these substrates not exceed about60 mrep. At constant temperature the degree to which the substrate isaffected by the polyorganosiloxane graft copolymerized to it will dependupon the nature of the substrate, the nature of the polyorganosiloxanegraft copolymerized and the amount of irradiation to which the textilebearing the polyorganosiloxane is subjected. The concentration of thepolyorganosiloxane upon the substrate will also affect the ultimateresults. In general the polyorganosiloxanes are applied to the substrateas liquids or solutions, the solutions being of relatively highconcentration. Such procedure provides the maximum opportunity for thepolyorganosiloxanes to be bombarded by the high energy particle.

Prior to treatment, the shaped article, such as a filament, may beoriented by hot or cold drawing. It may contain fillers such aspigments, antioxidants, polymerization catalysts and the like. After theirradiation the prod uct may be after-treated. Frequently a certainamount of decomposition occurs at the surface which is readily removedby washing in detergent. In other a'fter-treatments, the textile may bedyed, bleached hot or cold drawn, chemically reacted, or given coatingsof lubricants, sizes or the like or other similar treatments.

To be eificient in the practice of the present invention, it isnecessary that the radiation have sufiicient velocities to permitpenetration of several layers of material, when fabrics or films arebeing treated. The velocity required will depend on the nature of theparticle and also on the nature of the substrate to a certain extent. Anelectron particle which is under acceleration by a potential of amillion volts (mev.) will penetrate a thickness of polyhexamethyleneadipamide of about 0.25 cm. regardless of the form of the shapedarticle, i.e., the nature of the weave, denier or filament, whether thetextile is solid, or a fabric formed from filamentous materials.Acceleration -of electrons by 2 mev. will penetrate a shaped articlehaving a thickness of /2 cm. In situations where surface efiects areparamount, it is not necessary that the textile be completely penetratedby the high energy particle and lower accelerations may be employed.Under these conditions, if the surface effect is to be applied to bothsides of the shaped article, it will obviously be necessary to exposeeach of the surfaces to the particle radiation. This is done bysimultaneously bombarding both sides of the shaped article oralternatively by subjecting each side to the single source ofirradiation during different runs.

The polyorganosiloxane may be applied to its shaped substrate byimmersion, padding, calendering, spraying,

exposure to vapor condensation, or by other similar means. It issometimes desirable to remove excess liquid by squeezing prior toexposure to irradiation. Alternatively, the polyorganosiloxane may bedeposited upon the textile substrate by flashing off the solvent inwhich it is dissolved prior to application.

The process of the present invention is valuable in creating surfaceeffects upon textiles. It may be employed upon textiles to affectsoftness, resilience, tendency to shrink, static propensity, dyeability,resistance to hole melting, pilling, hydrophilicity, wickabili'ty, andthe like. It is useful in varying such properties as tenacity,elongation, modulus, creep, compliance ratio, work recovery, tensilerecovery, decay of stress, wet properties, hightemperature properties,abrasion and Wear resistance, moisture regain, flex life, hydrolyticstability, heat-setting properties, boil-off shrinkage, dry-cleaningproperties, heat stability, light durability, zero strength temperature,melting point, soilability, ease of soil removal, laundering propties,liveliness, crease resistance, torsional. properties, hysteresisproperties, fiber friction, dyeability (depth, rate, permanence anduniformity), printability, washfastness of dyes or finishing treatments(resins, ultraviolet absorbers, etc.), handle and drape properties(stiffening or softening), pilling, heat-yellowing, snag resistance,elasticity, density, ease in textile processability, solubility(insolubilization or increase in solubility), bleachability, surfacereactivity, delustering action, drying properties, fabric life,crimpability, stretchability, fabric stabilization, compressionalresilience (rugs), thermal and electrical conductivity, transparency,light transmittance, air and water permeability, fabric comfort,felting, ion exchange properties, adhesion, over-all appearance andcombinations of these as well as others.

In addition to the above modifications there are other modificationswhich would be particularly useful in fabrics and synthetic papers. Byway of illustration, fabrics may be modified to improve adhesion tovarious coating or laminating agents which it may be desirable to adherethereto, to change slip" or the ease with which one sheet slides overanother, to produce non-reflective or decorative coatings on fabrics orsheets, to improve the ease of printing colors on such sheets and manyother modifications such as will readily suggest themselves to oneskilled in the ,art.

It is apparent that those properties which are not primarily a functionof surface characteristics (e.'g., tenacity, elongation, modulus, andthe like) may be more conveniently modified by incorporating themodifiers in the polymeric matrix of the textile and then subjecting itto particle irradiation to develop adherence. It is also apparent thatat times it may be desirable to incorporate one or more modifiers in thematrix and coat one or more modifiers on the surface of the polymer,then develop adherence simultaneously by irradiating the shaped textilearticle.

Many other modifications will be apparent to those skilled in the artfrom a reading of the above description without a departure from theinventive concept.

What is claimed is:

1. A Water repellant textile for-med from a polyamide selected from alinear polyamide containing recurring units of the formula NZC wherein Zis a member of the class consisting of a divalent (hydrocarbon radicaland divalent radical of the formula II 0 innin wherein G and G aredivalent hydrocarbon radicals, having a po'lyo'rganosiloxanegraft-polymerized thereto, the said polyorgano'siloxane being graftpolymerized to the said linear polyarnide by ionizing radiation havingan energy from about 50,000 ev. to about 100 mev. at a radiation dose offrom about 0.05 mrep to about 80 rnrep.

2. The structure of claim 1 wherein the said textile is in the form of afabric.

3. The structure of claim 1 wherein said textile is in the form of ayarn spun from staple fiber.

4. The structure of claim 1 wherein the said textile is in the dorm of acontinuous filament.

5. The structure of claim 1 wherein the said textile contains at least0.001% polyonganosiloxane as the cograft-polymerized constituent of thesaid polyarnide.

References Cited by the Examiner UNITED STATES PATENTS 2,955,95310/1'960 Graham 204154 2,959,569 11/1960 Warrick. 3,097,960 7/1963Lawton et al.

FOREIGN PATENTS 758,735 10/1956 Great Britain. 83 8,412 4/ 1956 GreatBritain.

OTHER REFERENCES Pinner, S. H., and Wyc-herley, V.: Plastics, January1958, pp. 27-30.

NORMAN G. TORCHIN, Primary Examiner.

JULIAN S. LEVITT, Examiner.

I. CANNON, Assistant Examiner.

1. A WATER REPELLANT TEXTILE FORMED FROM A POLYAMIDE SELECTED FROM ALINEAR POLYAMIDE CONTAINING RECURRING UNITS OF THE FORMULA-N-Z-COWHEREIN Z IS A MEMBER OF THE CLASS CONSISTING OF A DIVALENTHYDROCARBON RADICAL AND DIVALENT RADICAL OF THE FORMULA-G-NH-CO-G''WHEREIN G AND G'' ARE DIVALENT HYDROCARBON RADICALS, HAVINGA POLYORGANOSILOXANE GRAFT-POLYMERIZED THERETO, THE SAIDPOLYORGANOSILOXANE BEING GRAFT POLYMERIZED TO THE SAID LINEAR POLYAMIDEBY IONIZING RADIATION HAVING AN ENERGY FROM ABOUT 50,000 EV. TO ABOUT100 MEV. AT A RADIATION DOSE OF FROM ABOUT 0.05 MREP TO ABOUT 80 MREP.